The UK government faces losing £120m if its plan to deport asylum seekers to Rwanda is ruled unlawful by the courts.
The scheme was announced in April, with the government claiming it would deter people from making dangerous crossings over the English Channel.
But the first flight was grounded in June after last minute legal challenges, and new court documents released this week showed officials had warned Home Secretary Priti Patel against going ahead with the plan.
Several asylum seekers, the Public and Commercial Services union and a number of charities are challenging the legality of the policy, with court hearings set for September and October.
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Downing Street admitted last month that some money had already been paid to Rwanda for the scheme, but refused to say how much, claiming the information was “confidential”.
But on Friday, Rwandan government spokeswoman Yolande Makolo confirmed there had been “an initial transfer of £120m”, adding: “This has already been paid, and we are already using the funds to prepare.”
Asked if the money would be repaid if UK courts blocked the scheme, Ms Makolo said: “It’s paid over, it’s committed. Part of it has been used.”
She also insisted the country remained “committed” to the partnership, adding: “We are determined to make it work.”
The chief adviser to the Rwandan justice minister, Doris Uwicyeza Picard, also told reporters: “We are confident in the legality of this partnership.”
Earlier this week, the Commons Home Affairs Committee said there was “no evidence” the policy was acting as a deterrent for Channel crossings, with more than 1,000 migrants making the journey since it was announced.
Labour’s shadow home secretary, Yvette Cooper, said the government’s plan was a “total mess”.
But on Thursday, a UK government spokesperson said: “Rwanda is a safe and secure country with a track record of supporting asylum seekers.
“We remain committed to delivering this policy to break the business model of criminal gangs and save lives.”